Development of an effective self-cleaning system to minimize fouling in heat exchangers

Power plant steam condensers use cooling water for condensation of exhaust steam from turbines. Depending on the concentration of cations in the cooling water, changes in temperature result in the precipitation of insoluble metal salts on the tube walls hence impeding heat transfer, leading to fouling, a threat on the heat transfer efficiency of the condenser. The research was carried out at a power station in Zimbabwe where offline mechanical methods used to clean the tubes were observed to be slow and inefficient, hence increasing downtimes. The use of spherical rubber balls was proposed where they were injected into the cooling water to scrub off dirt on the tube surfaces as well as creating turbulence to prevent the dirt from settling on the tube walls. Ball sizes of diameter less than the tube sizes were preferred in order to cater for possible thermal expansion of the rubber material on exposure to elevated temperatures. A magnetic water treatment unit was added to facilitate the formation of weak precipitates of the metal salts for ease of removal on cleaning. The design and implementation of the research results had the potential of saving the company on downtimes during condenser cleaning.